Remnants in the adiabatic or Sedov expansion phase are typically bright at X-ray wavelengths, owing to both the hot ISM gas shocked by the forward shock and the hot ejecta shocked by the reverse shock. In Figure REF , we show a canonical example of a remnant in this phase: DEM L71, a remnant in the LMC believed to be a few thousand years post-explosion [1]}, [2]}.
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